Throttle pedal controlled pneumatically operated throttle override

ABSTRACT

A pneumatically operated valve is mounted on the air horn of a carburetor and is operable in a normal condition to fully open a carburetor air inlet and in an alternative throttle override condition to limit the air flowing through the inlet and thereby throttle the engine down to an idling speed. A control valve is operated by the vehicle throttle pedal to control the communication of engine vacuum to the pneumatically operated air inlet valve to normally establish the normal condition when the throttle pedal is depressed and the alternative override condition when the throttle pedal is released.

0 United States Patent 11 1 1111 3,738,347 Stoltman June 12, 1973 THROTTLE PEDAL CONTROLLED 3,699,943 10/1972 Eshelman 123/198 DB PNEUMATICALLY OPERATED THROTTLE 3,698,372 10/1972 Eshelman et al. 123/198 DB OVERRIDE Donald D. Stoltman, Henrietta, N.Y.

General Motors Corporation, Detroit, Mich.

Filed: Feb. 14, 1972 Appl. No.: 226,075

Inventor:

Assignee:

References Cited UNITED STATES PATENTS 12/1971 MacMillan 123/198 DB 7/1972 Hensler 123/198 D X Primary ExaminerAl Lawrence Smith Attorney-E. W. Christen, .I. L. Carpenter and R. L. Phillips [57] ABSTRACT A pneumatically operated valve is mounted on the air horn of a carburetor and is operable in a normal condition to fully open a carburetor air inlet and in an alternative throttle override condition to limit the air flowing through the inlet and thereby throttle the engine down to an idling speed. A control valve is operated by the vehicle throttle pedal to control the communication of engine vacuum to the pneumatically operated air inlet valve to normally establish the normal condition when the throttle pedal is depressed and the alternative override condition when the throttle pedal is released.

7 Claims, 12 Drawing Figures PMENTUI 3.738.347

SEE? 3 U 3 I K 22a 218 THROTTLE PEDAL CONTROLLED PNEUMATICALLY OPERATED THROTTLE OVERRIDE This invention relates to throttle controls for internal combustion engine carburetors and more particularly to throttle controls for controlling the air drawn into a carburetor when normal movement of the throttle valve is prevented.

The present invention provides a differential pressure-operated air inlet valve that is mounted on the air horn of an internal combustion engine carburetor and that includes a disc-shaped limiter plate which in a normal condition is raised above the air horn to fully open the air inlet to the air horn and in an alternative throttle override condition is lowered onto the air horn to limit the air flow through the air inlet and thereby throttle the engine down to an idling speed. A conduit communicates the air inlet valve and a vacuum port in the throttle bore of the carburetor with a control valve that is closed by depression of the throttle pedal to establish the normal condition. Release of the throttle pedal opens the control valve to establish the throttle override condition should the throttle valve be prevented from normally returning to its idle position.

In one illustration of the invention, the limiter plate is spring lowered to close the air inlet and vacuum raised to normally open the inlet. The control valve when closed communicates vacuum to the inlet valve from a port located just downstream of the idle position of the carburetor throttle valve. Opening the control valve with the throttle open bleeds the vacuum in the air inlet valve, thereby allowing the limiter plate to be spring lowered onto the air inlet. Pivotably attached to the limiter is an air flow responsive latch that, during normal engine turn-off operations, pivots between the limiter plate and the air horn. The latch thus prevents the limiter plate from seating directly on the air horn and thereby allows sufficient air to be drawn into the carburetor to avoid the fuel rich engine restart conditions otherwise created by fuel vapors produced by the engine heat remaining after a prior engine turn-off. Should the control valve be opened to lower the limiter plate when the engine is not normally shut off, such as when the throttle valve is restrained from being normally returned to its idle position by a return spring, the air flow associated with the open throttle valve deflects the latch out of the closing path of the limiter to permit the limiter plate to seat directly on the air horn. Apertures through thelimiter plate then allow a proper flow of air to be drawn into the carburetor to sustain engine idling operation.

In another illustration of the invention, the limiter plate is spring raised to normally open the inlet and is vacuum lowered to close the inlet. The control valve when open contacts the air inlet valve in series with a vacuum port located just upstream of the throttle valve when in its idle position. This location of the vacuum port avoids the communication of engine vacuum to the air inlet valve when the throttle valve is in its idle position and thereby permits normal engine starting and idling operation even though the control valve is open. However, should the control valve be closed with the throttle valve not normally returned to its idle position, engine vacuum is communicated to the air inlet valve to overcome the spring opening bias on the limiter plate to seat the limiter directly on the air horn. Ap-

ertures through the limiter plate then admit sufficient air flow to sustain idle operation.

It is therefore an object of the present invention to provide a pneumatically operated air inlet valve for limiting the air admitted to the air inlet of an internal combustion engine carburetor when the carburetor throttle valve is not normally returned to its idle position, the inlet valve being operated with engine vacuum under the control of a control valve operated by the vehicle throttle pedal.

It is another object of the present invention to provide in an air inlet valve of the foregoing type an air flow limiter plate that, during depression of the throttle pedal, is normally vacuum raised above the air inlet so as to not impede the air drawn into the engine and that, with the throttle pedal released, is spring lowered to limit the air drawn into the inlet so as to throttle the engine to an idling speed.

It is a further object of the present invention to provide, in an air inlet valve of the foregoing type, a flow responsive latch carried by the limiter plate and deflected out of its closing path when the throttle valve is not in its idle position to allow the limiter to seat directly on the carburetor air inlet, the latch being pivoted into the closing path to prevent such direct seating upon a normal engine turn-off to avoid the fuel rich engine restart conditions otherwise created by fuel vapors produced by engine heat remaining after a prior engine shut-off.

It is a further object of the present invention to provide an engine vacuum operated air inlet valve for limiting the air admitted to the air inlet of an internal combustion engine carburetor when the carburetor throttle valve is not normally returned to its idle position wherein the inlet valve has an air flow limiter plate that is spring raised to normally open the air inlet so as to not impede the flow of air being drawn into the engine and that is vacuum lowered to close the air inlet when engine vacuum is communicated to the air inlet valve under the control of a control valve operated by a vehicle throttle pedal.

It is a further object of the present invention to provide an air inlet valve of the foregoing type wherein the control valve when open connects the air inlet valve in series with a port in the carburetor just upstream of the throttle valve when in its idle position so that the air inlet valve remains open during engine starting and idle operations with the throttle pedal released.

These and further objects and features of the present invention will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a view partly in schematic and partly in cross-section of an internal combustion engine carburetor throttle control provided in accordance with the present invention including a throttle pedal-operated control valve and a pneumatically operated air inlet valve having an air flow limiter plate for opening and closing a carburetor air inlet;

FIG. la is a view of an alternative embodiment of the throttle pedal operated control valve of FIG. 1;

FIG. 2 is a view partly in cross-section taken along section 2-2 of FIG. 6 of the pneumatically operated air inlet valve of FIG. 1 in a condition wherein the limiter plate is raised above the carburetor air inlet and pivotably supports a deflectable latch;

FIG. 3 is another view of the pneumatically operated air inlet valve of FIG. 1 in a condition wherein the lim iter plate is seated directly on the air inlet and the latch does not engage the carburetor;

FIG. 4 is a cross-sectional side view of the latch of FIGS. 2 and 3 in a position engaging the carburetor;

FIG. 5 is another view partly in cross-section taken along section 55 of FIG. 4 of the latch of FIGS. 2, 3 and 4;

FIG. 6 is a plan view taken along section 6-6 of the air inlet valve of FIG. 2;

FIG. 7 is a plan view taken along section 77 of the air inlet valve of FIG. 2;

FIG. 8 is a view partially in cross-section and partially in schematic of an alternative throttle pedal and control valve structure for operating the air inlet valve shown in FIG. 1;

FIG. 9 is a view partially in cross-section and partially in schematic of an alternate throttle control provided in accordance with the present invention and including a throttle pedal operated control valve and a pneumatically operated air inlet valve having an air flow limiter plate shown in a position closing the air inlet of an internal combustion engine carburetor;

FIG. 9a is a view of an alternative embodiment of the throttle pedal operated control valve of FIG. 9; and

FIG. 10 is a view of the throttle control of FIG. 9 in a condition wherein the limiter plate is raised above the carburetor air inlet.

DESCRIPTION OF THE EMBODIMENT OF FIGS. 1, 2, 3, 4, 5, 6, AND 7 With reference now to FIG. 1, there is shown an air horn 10 having a choke valve 12 pivotable in an air inlet opening 14 to admit a flow of air to a throttle bore 16 of an internal combustion engine carburetor 18 suitably secured to an internal combustion engine 20. Carburetor 18 has a throttle valve 22 for controlling the flow of air drawn into an induction passage 24 of engine through an air cleaner 26 having a floor 28 seated on an annular rim 30 about the periphery of air horn 10.

To override throttle valve 22 when it is prevented from normally returning to an idle position, the flow of air into inlet 14 is limited by an air inlet valve 32. Air inlet valve 32, as described in further detail below, is mounted on an air horn 10 above inlet 14 and includes a vacuum chamber 34 and a spring 36 preloaded therein for vacuum raising and spring lowering an air flow limiter plate 38 relative to an air horn top surface 40 bounding the inner periphery of air inlet opening 14.

Throttle valve 22 is pivotable on a throttle shaft 42 between an idle position 23'shown solid and a wide open throttle position 23' shown dotted by throttle linkage 43 including a throttle lever 44 connected to rotate with shaft 42. Connected between a return spring bracket 46 suitably connected to engine 20 and throttle lever 44 is a return spring 48 that normally biases throttle lever 44 in a valve closing direction, counterclockwise as viewed in FIG. 1, to return throttle valve 22 to its idle position 23. Also connected to throttle lever 44 by a throttle rod 50 is one end of a throttle pedal 52 having an intermediate yoke section 54 displaceable along and pivotable about a support 56 secured to a firewall 58. Spring biased by a valve spring 60 to follow the motion of the left side of yoke section 54 is the stem 61 of a movable valve element 62 of 'a bleed control valve 64. Control valve 64 is biased open by spring 60 when the operator does not apply force to pedal 52 so that it is released. When the operator applies force to pedal 52 so that it is depressed, control valve 64 is closed by valve element 62 when pushed by yoke 54 as it is caused to slide on support 56 by pedal 52. After bleed control valve 64 is thus closed, yoke 54, while still holding valve element 62 to close valve 64, pivots on the end of stem 61 as pedal 52 pulls throttle rod 50 to overcome the return bias of return spring 48 and pivot throttle valve 22 in a valve opening direction, clockwise as viewed in FIG. 1.

Located in throttle bore 16 just downstream of throttle valve 22 when in its idle position 23 are a pair of diametrically opposed flow restriction ports 66 and 67 respectively arranged to be upstream and downstream of throttle valve 22 when in a position 23" intermediate its idle and wide open positions 23 and 23. To control the communication of engine vacuum between throttle bore 16 and vacuum chamber 34, bleed control valve 64 is connected by a bleed conduit 68 to communicate with a vacuum communication path designated generally at 69. Communication path 69 includes a first passage 70 in air inlet valve 32, an air horn-to-air valve connection fitting 72 communicating between first passage 70 and a second passage 74 in air horn 10, a first nipple fitting 76 threaded into air horn 10 just below air cleaner receiving rim 30 and communicating second passage 74 with conduit 68 through a vacuum bleed conduit 78, and a pair of vacuum conduits 80 and 82 connected to communicate conduit 78 with ports 66 and 67 respectively through second and third nipple fittings 84 and 85 threaded into carburetor 18.

As may be better understood in conjunction with FIGS. 2, 3, and 4, air inlet valve 32 includes a diaphragm assembly retained in a generally cylindrical valve body 86 that is supported centrally over air inlet opening 14 by a pair of studs 88 and 90. Valve body 86 includes a top 92 integral with an axially extending cylindrical side 94 and side 94 has a pair of diametrically opposed ears 96 and 98 supported by studs 88 and 90. Passage 70, as seen in FIG. 1, extends axially along a portion of the length of ear 98 and then radially through the inner surface of side 94 into vacuum chamber 34.

As best seen in FIGS. 2 and 3, each stud 88 and has a hexagonal shank portion 100 for threading a threaded bottom end 102 into one of two diametrically opposed threaded holes 104 and 106 extending axially into a top surface 40 on opposite sides of inlet opening 14. Each stud also has a reduced diameter portion 108 that passes through a bore 110 or 112 in body ears 96 and 98, respectively, and provides with hexagonal portion 100 a shoulder 114 that cooperates with ears 96 and 98 to support inlet valve 32 axially above air horn 10 so that body 86 is centrally located over air inlet opening 14. Each stud also has a threaded top end 116 that extends through an opening 118 in roof 120 of air cleaner 26 to threadably receive a nut 122. Nut 122 is threaded down on threaded top end 116 of each stud to secureair cleaner 26 against axial displacement relative to air born 10 by biasing roof 120 so that an air cleaner floor 28 sealingly seats on air horn rim 30. To secure valve body 86 against axial movement relative to air horn 10, a flat body retainer 124 is spring fitted between studs 88 and 90 into a neck portion 126 thereofintermediate reduced diameter portion 108 and threaded top end 116.

The diaphragm assembly, as best seen in FIGS. 2 and 3, includes a disc-shaped flexible diaphragm 130 that has an annular peripheral outer welt 132 sealingly retained by a crimpable diaphragm retainer 134 in an annular retaining seat 136 on the exterior of one end of body side 94. Limiter plate 38 is riveted to a spring cup 138 by a rivet 140 having an axial portion 142 between limiter 38 and cup 138 on which an annular central inner welt 144 of diaphragm 130 is sealingly seated, and valve body 86, diaphragm 130, and rivet portion 142 thus define vacuum chamber 34. Spring 36 is compressed in this chamber between body top 92 and spring cup 138 and biases limiter plate 38 downwards towards top surface 40 of air horn l whenever the effect of the spring is not overcome by the pressure differential across diaphragm 130.

As best seen in FIG. 6, the outer periphery of limiter plate 38 extends beyond the inner perimeter of air inlet opening 14 to everywhere overlap top surface 40 and is generally circular except for cutouts about studs 88 and 90. Limiter plate 38 may therefore be moved freely between a fully raised position shown in FIG. 2 in which it does not impede the flow of air drawn into inlet 14 by engine 20 and a fully lowered position shown in FIG. 3 in which it seats directly on the top surface 40 to substantially close air inlet 14. To avoid engine shut down when limiter plate 38 seats directly on top surface 40, limiter 38 has a first pair of axial apertures 146 and 148 for admitting sufficient air to sustain idle engine operation and a second pair of apertures '150 and 151 for respectively providing a good fuel distribution in throttle bore 16 and for compensating the pressure in the float bowl during such idle. However should limiter 38 be allowed to seat directly on top surface 40 as the result of a normal engine shut down, apertures 146 and 148 and apertures 150 and 151 by themselves would not admit sufficient air to properly burn the rich fuel mixture created by the fuel vapors evaporated in the hot soak of the engine heat remaining after a normal engine turn-off. Therefore, to allow sufficient additional air to be drawn into carburetor 18 to permit satisfactory restart in the hot soak period after a normal shut down, limiter plate 38 pivotably carries an air flow deflectable sheet metal latch 152 that upon normal engine shut down swings into the closing path of limiter 38 to engage top surface 40 and prevent limiter 38 from seating directly thereon.

Latch 152, as best seen in FIGS. 4 and but as also seen in FIGS. 2, 3, and 6, is inserted downward towards air horn through a slot 154 in limiter 38 at a point thereon circumferentially intermediate body ears 96 and 98 and at a radius slightly less than the inner lip of air inlet 14 so that a length section 156 of latch 152 clears the inner perimeter of inlet 14, as seen in FIG. 4, when limiter 38 is lowered during normal engine shut down. Length section 156 is terminated at one end by a pair of T-shaped flanges 158 and 160 resting on the top surface of limiter plate 38 and pivotably supporting latch 152 therefrom through slot 154 in the path of air drawn out from air inlet 14. Latch 152 is deflected towards the center of limiter 38 as seen in FIG. 4 when air is drawn into inlet 14 at a rate in excess of that normally required for restarting engine 20. Such excess air flow is drawn whenever engine runs with throttle valve 22 not in its idle position, both when throttle valve 22 is normally controlled by throttle pedal 52 and when prevented from being normally returned to its idle position. However, to prevent the direct seating of limiter 38 on top surface 40 at air flows less than that required for restarting, latch 152 includes a latch portion 162 and a bent portion 164 that cooperates with latch portion 162 to support limiter plate 38 above top surface 40. Latch portion 162 is bent at right angles out of the plane of length section 156 so as to engage and rest on top surface 40 when limiter 38 is lowered, and bent portion 164 is bent at less than a right angle out of the plane of length section 156 towards the outer edge of limiter 38 so as to engage the bottom surface thereof when lowered, as seen in FIGS. 2, 4 and 5. Bent portion 164 also cooperates with the bottom surface of limiter 38 to prevent counterclockwise rotation of latch 152 past a vertical position so as to prevent the bottom of length section 156 from catching on top surface 40 and interfering with the downward movement of limiter 38 when the flow of air into inlet 14 is insufficient to deflect latch 152 inwards.

OPERATION OF FIG. 1 EMBODIMENT Prior to start of engine 20 after a normal engine turnoff, atmospheric pressure exists on both sides of diaphragm so that spring 36 extends limiter plate 38 towards air horn 10 and latch 152 engages the top surface 40 as shown in FIGS. 4 and 5. During normal starting and running of engine 20, air in vacuum chamber 34 is drawn into engine induction passage 24 through the vacuum communication path 69 including inlet valve passage 70, fitting 72, air horn passage 74, fitting 76, vacuum bleed conduit 78, vacuum conduit 82, fitting 85, and vacuum port 67. The pressure in vacuum chamber 34 is reduced so that the resulting pressure differential across diaphragm 130 allows the atmospheric pressure on the outside of diaphragm 130 to overcome the downward bias of spring 36 on cup 138 and raise limiter 38. Limiter 38 is then raised until it abuts valve body 86 where it fully opens air inlet 14 as seen in FIG. 2. The air drawn from vacuum chamber 34 into throttle bore 16 during normal starting and running of engine 20 establishes a vacuum sufficient to raise and then retain limiter 38 in its fully open position regardless of whether pedal 52 is in a released position wherein control valve 64 admits air to conduit 78 or whether pedal 52 is in a depressed position wherein port 66, being upstream of intermediate position 23" of throttle valve 22, is exposed to a higher pressure than port 67. Thus, with the release of throttle pedal 52 the vacuum required to overcome the loss through open valve 64 and to raise limiter 38 is drawn through ports 66 and 67, both such ports being exposed to the low pressure downstream of idle position 23 of throttle valve 22. Depressing pedal 52, while closing control valve 64 to eliminate one loss of vacuum, introduces another loss by moving throttle valve 22 to an intermediate position 23" where port 66 now being upstream of valve 22 is exposed to a higher pressure than port 67. Thus, when pedal 52 is depressed the vacuum required to raise limiter 38 is drawn primarily through port 67 which is exposed to the lower pressure downstream of throttle valve 22.

The pressure differential across diaphragm 130 falls to allow the limiter 38 to be lowered when control valve 64 and port 66 are exposed to atmospheric pressure as upon a normal shut-off of engine 20. This condition is also established with engine 20 running when throttle linkage 43 including lever 44, spring 48, rod 50, and pedal 52, rather than normally returning throttle valve 22 to its idle position 23, retains it in intermediate position 23". Being upstream of throttle valve 22 and therefore at a higher pressure than port 67 which is downstream, port 66 and control valve 64 when open bleed off enough of the vacuum still being drawn through port 67 to lower the pressure in chamber 34. When the pressure differential across diaphragm 130 has been thus decreased to a point where the bias of spring 36 is no longer overcome, spring 36 extends to urge limiter 38 downwards towards air horn top surface 40. Whether or not latch 152 engages top surface 40 as limiter 38 approaches air horn depends on whether throttle valve 22 is normally returned to its idle position upon the release of pedal 52 or whether throttle valve 22 is not returned to its idle position because throttle pedal linkage 43 is prevented from properly moving throttle valve 22 in a valve closing direction.

Should throttle valve 22 be normally returned to its idle position, the air drawn past deflectable latch 152 into inlet 14 is not sufficient to deflect latch 152 out of the closing path of limiter 38. Right angle latch section 162 then engages the top surface 40 of air horn 10 and cooperates with angularly bent section 164 to support limiter 38 at a height axially intermediate its fully raised and fully lowered positions above air horn top surface 40, as shown in FIGS. 3, 4 and 5, thereby creating a larger passage for the admittance of air to air inlet 14 than would be created if limiter 38 were permitted to seat directly on top surface 40. Should engine be shut off with limiter 38 in this latched condition, any fuel vapors that might be evaporated in the hot soak of the engine heat remaining after a normal engine shutoff would, upon a subsequent engine restart, be mixed with a sufficient flow of air to provide a proper air-fuel ratio sustain engine operation without stalling.

However, should throttle valve 22 stay in an intermediate position 23" upon release of throttle pedal 52, the air drawn into induction passage 24 through inlet 14 would be sufficient to deflect latch 152 clockwise towards the center of limiter 38 out of the closing path thereof so that spring 36 biases limiter 38 to seat directly on top surface 40 of air horn 10, as shown in FIG. 3. With limiter plate 38 thus seated, sufficient air to sustain idle operation of engine 20 is drawn through idle holes 146, 148, 150, and 151 thereby assuring the availability of power to operate other vehicle accessories including, for example, the vehicle power steering system and the vehicle power brake system.

DESCRIPTION OF PEDAL EMBODIMENT OF FIG. 8

An alternate throttle pedal-control valve arrangement 170 for opening inlet valve 32 is shown in FIG. 8. Therein, a throttle pedal level 172 is pivotably supported from a firewall 58 by a pivot 173 so that, when rotated in a clockwise direction as viewed in FIG. 8, one end of throttle pedal level 172 engages throttle rod 50 to move throttle valve 22 in the opening direction. The other end of lever 172 includes a pedal contact pad 174 that is engageable by a protrusion 176 at the end of a throttle pedal 178 pivotably connected by a pivot 180 to firewall 58 near floor board 59. Intermediate the pivot and contact ends of pedal 178 are a pair of hose openings 182 and 184 separated radially between pro- 184 to provide a bight section 192 along bight support 186.

A hose crimp member 194 is secured to be pivotable with and relative to pedal 178 by a stud 195 that proj ects from crimp member 194 toward firewall 58. Stud 195 extends slippingly through a stud hole 196 in pedal 178 and is threadably secured on the other side of pedal 178 by a nut 197 so as to let stud 195 translate slightly through hole 196 while also affixing crimp member 194 loosely to pedal 178. Crimp member 194 has a hose crimping rib 198 extending towards bight support 186 of pedal 178 in juxtaposition to bight section 192 of hose 188. When foot pressure is applied to crimp member 194, crimping rib 198 cooperates with bight support 186 to crimp bight section 192 of hose 188 so as to prevent communication of atmospheric pressure from an atmospheric end 191 to conduit 68. When foot pressure is removed from crimp member 194, hose 188 due to its natural resiliency, forces crimp member 194 to pivot at stud 195 in a clockwise direction relative to pedal 178 to allow conduit 68 to communicate with atmosphere through atmospheric end 191 of hose 188.

DESCRIPTION OF EMBODIMENT OF FIGS. 9 AND 10 As may be better understood with reference to FIGS. 9 and 10, alternate apparatus for controlling the quantity of air admitted to the air inlet of a carburetor includes an inlet valve 200 located in an air cleaner assembly 201 having a floor 202 seated on an annular rim 203 of an air horn 204 and secured thereto by a pair of screws 205, only one of which is shown, passing through a roof 206 and threaded into an air horn wall 207. Air inlet valve 200 is pneumatically operated to vacuum lower and spring raise an air flow limiter plate 208 relative to a generally annular top surface 210 of air horn 204 bounding a generally annular air inlet opening 212 therethrough.

Air horn 204 is mounted on an internal combustion engine carburetor 213 having a throttle bore 214 communicating with air inlet opening 212 and with an induction passage 215 in an engine 216. Air horn 204 further includes a vacuum passage 217 in a valve support 218 that comprises radial portion 219 extending radially from air horn wall 207 and an axial portion 220 centrally located in air inlet opening 212 and extending axially towards top surface 210. Threadably received by axial portion 220 of valve support 218 is a threaded end 222 of a tubular post 224 torqued at a squareshaped shank section 226 and passing through a central aperture 228 in limiter 208. Snap fitted into a circumferential groove 230 at the other end of valve support post 224 is a spring cup 232 for receiving one end of a helical spring 234, the other end of which bears against the roof of a valve housing 236. Sealingly seated against the periphery of valve support post 224 between limiter 208 and spring cup 232 is a welted central opening 240 of a flexible disc-shaped diaphragm 238 that has a peripheral welt 242. Peripheral welt 242 is sealingly crimped by a crimpable flange 244 of cylindrical housing 236 against an annular retainer ring 248.

So that it may be translated axially with respect to air horn top surface 210 by the motion imparted to valve housing 236, limiter 208 is riveted by rivets 250 to four axially extending posts 252, only one of which is shown spaced equi-angularly about retainer ring 248 and extending axially therefrom toward top surface 210.

Diaphragm 238 being sealed at its inner welt 240 to valve support post 224 and at its outer welt 242 to valve housing 236 defines therewith a vacuum chamber 254.

Chamber 254 communicates with a first port 256 of a 10 valve body 257 of a control valve 258 by means of a communication path including post 224, passage 217, and a first conduit 260 connected between passage 217 and port 256. Valve body 257 has a second port 262 connected by a second conduit 264 to communicate port 256 and is biased leftwardly by a valve spring 274 to follow a yoke section 278 of a throttle pedal 280. Throttle pedal 280 is translatable and pivotable at yoke section 278 relative to support 282 secured to a firewall 284 so that with throttle pedal 280 released, port 256 is opened as valve spring 274 causes a stem 273 on valve element 272 to push yoke section 278 to the left as seen in FIG. 9. When throttle pedal 280 is depressed, yoke section 278 first translates to the right on support 282 so as to push stem 273 of valve element 272 to close port 256. With further depression of throttle 3O pedal 280, yoke section 278 pivots on the end of stem 273 in a counterclockwise direction as viewed in FIG. 9 while still holding valve element 272 to close valve port 256. When thus pivoted, throttle pedal 280 pulls a throttle rod 285 to rotate a throttle lever 286 connected to throttle valve 270 through a throttle shaft 288 in a valve closing direction against the return bias of a return spring 290 connected to a return spring bracket 292.

Control valve 258 is thus operative when throttle 4O pedal 280 is released to connect vacuum chamber 254 of air inlet valve 200 in series with port 266 through valve support post 224, air horn valve support structure 218, and connection conduits 260 and 264. Such connection, as explained in further detail below, allows 4 limiter 208 to be normally spring raised by spring 234 when the engine 216 is off or the throttle pedal 280 is depressed. Limiter 208 is lowered by the pressure differential across diaphragm 238 when, with the engine 216 running and the throttle valve 270 not normally returned to its idle position, throttle pedal 280 is released to allow a vacuum to be drawn in chamber 254 from port 266.

translates on support 282 before pedal 280 begins to pivot on stem 273 to translate throttle rod 285 in a valve opening direction. Depression of throttle pedal 280 in the engine starting operations therefore does not result in the communication of vacuum to vacuum chamber 254 so that spring 234 continues to retain limiter 208 in its normally raised position fully opening air inlet opening 212. Moreover, limiter 208 is retained in this position even if engine 216 is started with throttle pedal 280 released and the control valve 258 therefore biased open. Throttle valve 270 would then still be in its idle position so that port 266 is upstream of throttle valve 270 and there exposed to substantially the same pressure as on the outside of diaphragm 238.

When foot pressure is removed from throttle pedal 280, control valve spring 274 urges valve element 272 to follow the right side of yoke 278 to open valve port 256 as yoke 278 is translated to the left on support 282. Should throttle valve 270 be prevented from being normally returned to its idle position by return spring 290 upon the release of throttle pedal 280, port 266 would remain downstream of throttle valve 270 and would communicate engine vacuum to vacuum chamber 254. The engine vacuum creates a pressure differential across diaphragm 238 sufficient to overcome the valve opening bias of spring 234 and draws valve housing 236 downward to compress spring 234 and seat limiter 208 directly on top surface 210. When thus seated directly on air horn 24, limiter 208 is in a condition overriding the effect of an open throttle valve by limiting the flow of air into air inlet opening to a level just sufficient to sustain engine idling operation. Limiter 208, after being in this override condition, is returned to its normally raised position by turning off the engine to expose port 266 to atmospheric pressure and eliminating the pressure differential across diaphragm 238.

FURTHER ALTERNATE EMBODIMENTS The control valve 258, conduits 260 and 264, and pedal 280 shown in FIG. 9 could be replaced as shown in FIG. 9a by a structure similar to that shown in FIG. 8 merely by connecting end 190 of hose 188 therein to passage 219 and end 191 to port 266. Moreover, bleed 5 valve 64 and conduits 68, 78, 80 and 82 shown in FIG.

OPERATION OF EMBODIMENT OF FIGS. 9 AND Prior to a start or after a normal shut-off of engine 216, there is substantially no pressure differential across diaphragm 238 so that spring 234 is normally extended to raise limiter 208 to the upper limit of its travel, as shown in FIG. 10. In this position, air inlet opening 212 is fully open so that the air drawn therethrough for engine 216 as determined by the position of throttle valve 270 is not impeded by limiter 208. Starting of engine 216 does not create a pressure differential across diaphragm 238 since depression of throttle pedal 280 closes control valve 258 as yoke 278 1 could be replaced as shown in FIG. la by the control valve 258 and conduits 260 and 264 shown in FIG. 9 merely by connecting conduit 260 to air horn fitting 76 and conduit 264 to fitting 84 and closing port 67. With the latter modification, limiter 38 would be raised by engine vacuum communicated through just port 66 when throttle pedal 280 is released with throttle valve 22 in its idle position 23 and would be spring lowered by spring 36 whenever pedal 280 is released with valve 22 in its intermediate position 23".

Having described several embodiments of the present invention, it is understood that the specific terms and examples are employed in a descriptive sense only and not for the purpose of limitation. Other embodiments of the invention, modifications thereof, and alternatives thereto may be used. I therefore aim in the appended claims to cover such modifications and changes as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A throttle control for controlling the speed of an internal combustion engine comprising:

a. a carburetor having a throttle bore with an inlet admitting a flow of fluid, an outlet for communicating said fluid to said engine and communicating engine pressure to said throttle bore, a throttle valve pivotable in said throttle bore between a full open position and an idle position;

b. throttle linkage means for normally pivoting said throttle valve between said full open and idle positions and including return spring means for normally biasing said throttle valve to said idle position, said throttle linkage means further including a throttle pedal having an operative condition for pivoting said throttle valve in a valve opening direction against the bias of said return spring means and having an inoperative condition for allowing said return spring means to normally return said throttle valve to said idle position;

c. pneumatically operated valve means operated by said engine pressure and operable in a normal condition to fully open said inlet and alternatively in a throttle override condition to limit said fluid flow through said inlet so as to limit the speed of said engine to an idle speed;

d. conduit means for connecting said pneumatically operated valve means and said throttle bore; and e. override control valve means connected in said conduit means and operated by said throttle pedal to control the communication of said engine pressure between said throttle bore and said pneumatically operated valve means to normally establish said normal condition with said throttle pedal in said operative condition and to establish said override condition with said throttle pedal in said inoperative condition and said throttle linkage prevented from returning said throttle valve to its idle position.

2. A throttle control for controlling the speed of an internal combustion engine comprising:

a. a carburetor having a throttle bore, an inlet for admitting a flow of fluid to said throttle bore, an outlet for communicating fluid to said engine and communicating engine pressure to said throttle bore, a throttle valve pivotable in said throttle bore between a full open position and an idle position;

b. throttle linkage means for normally pivoting said throttle valve between said full open and idle positions and including return spring means for normally biasing said throttle valve means to said idle position, said throttle linkage means further including a throttle pedal having a depressed condition for pivoting said throttle valve in said valve opening direction against the return bias of said return spring means and having a released condition for allowing said return spring means to normally return said throttle valve to said idle position;

c. differential pressure operated valve means operable in a normal condition to fully open said inlet and alternatively, in a throttle override condition to limit said fluid flow through said inlet so as to limit the speed of said engine to an idle speed, said valve means including a pressure chamber, pressure conduit means connected between said vacuum chamber and said throttle bore, and fluid flow limiter means translatable between a raised position and a lowered position relative to said inlet for establishing said normal condition when in said raised position and said override condition when in said lowered position; and d. throttle override control valve means connected in said pressure conduit means and operated by said v throttle pedal to control the communication of said engine vacuum from said throttle bore to said pressure chamber through said vacuum conduit to normally establish said normal condition with said throttle pedal in said depressed condition and to establish said throttle override condition with said throttle pedal in said released condition and said throttle linkage means prevented from returning said throttle valve to said idle position. v

3. A throttle control for controlling the speed of an internal combustion engine comprising:

a. a carburetor having a throttle bore, an inlet for admitting a flow of fluid to said throttle bore, an outlet for communicating said fluid to said engine and communicating engine pressure to said throttle bore, a throttle valve pivotable in said throttle bore between a full open position and an idle position;

b. throttle linkage means for normally pivoting said throttle valve between said full open and said idle positions and including return spring means for normally biasing said throttle valve means to said idle position, said throttle linkage further including a throttle pedal having a depressed condition for pivoting said throttle valve in a valve opening direction against the return bias of said return spring means and having a release condition for allowing said return spring means to normally return said throttle valve to said idle position;

c. differential pressure operated valve means operable in a normal condition to fully open said inlet and alternatively in a throttle override condition to limit said flow through said inlet so as to limit the speed of said engine to an idle speed, said valve means including a pressure chamber, a conduit connected between said pressure chamber and said throttle bore, fluid flow limiter means translatable between a raised position and a lowered position relative to said inlet for establishing said normal condition when in said raised position and said override condition when in said lowered position, and latch means for supporting said limiter means in a position intermediate said raised and lowered positions when the fluid flow through said inlet is less than a predetermined flow; and

d. throttle override control valve means connected in said conduit and operated by said throttle pedal for controlling the communication of said engine pressure from said throttle bore to said pressure chamber to normally establish said normal condition with said throttle pedal in said depressed condition and to establish said throttle override'condition with said throttle pedal in said released condition and said throttle linkage means prevented from returning said throttle valve to said idle position.

60 4. A throttle control for controlling the speed of an internal combustion engine comprising:

a. a carburetor having a throttle bore, an inlet for admitting a flow of air to said throttle bore, an outlet for communicating said flow to said engine while also communicating engine vacuum to said throttle bore, throttle valve means pivotable in said throttle bore between an idle position and a full open position;

b. throttle linkage means including return spring means for normally biasing said throttle valve to said idle position and a throttle pedal having a depressed condition for pivoting said throttle valve in a throttle opening direction against the bias of said return spring means and having a released condition for allowing said return spring means to normally return said throttle valve to said idle position;

0. differential pressure operated fluid motor means operable in a normal condition to fully open said inlet and in an alternative throttle override condition to limit the flow of fluid through said inlet so as to limit the speed of said engine to an idle speed, said fluid motor means fixedly supported above said inlet, a diaphragm retained by said body and defining a pressure chamber therewith, a flow limiter connected to said diaphragm and translatable between a raised position and a lowered position relative to said inlet to respectively establish said normal and override conditions, conduit means connecting said pressure chamber and a port in said throttle bore intermediate said idle position and said outlet for positioning said limiter in said raised position when the pressure in said chamber effects greater than a predetermined pressure differential across said diaphragm, and a spring in said pressure chamber for positioning said limiter in said lowered position when said pressure differential is less than said predetermined pressure differential; and

d. throttle override control valve means connected in said conduit and operated by said throttle pedal, said control valve means, with said throttle pedal in said released condition and with said throttle linkage prevented from returning said throttle valve to its idle position, having an open condition for reducing said pressure differential below said predetermined pressure differential to establish said override condition.

5. A throttle control as set forth in claim 4 wherein, with said override control valve means in said open condition, said pressure chamber communicates freely with atmospheric pressure.

6. A throttle control as set forth in claim 4 wherein, with said throttle override control valve means in said open condition, said pressure chamber communicates freely with said port.

7. A throttle control for controlling the speed of an internal combustion engine comprising:

a. a carburetor having a throttle bore, an inlet for admitting a flow of air to said throttle bore, an outlet for communicating said flow to said engine while also communicating engine pressure to said throttle bore, a throttle valve pivotable in said throttle bore between an idle position and an open position;

b. throttle linkage means for pivoting said throttle valve between said idle and said open positions and including a return spring for normally biasing said differential pressure operated fluid motor means operable in a normal condition to fully open said inlet and in an alternative throttle override condition to limit the flow of said fluid through said inlet so as to limit the speed of said engine to an idle speed, said valve means including a diaphragm having a central portion fixedly supported above said inlet, a housing sealingly secured to said diaphragm and defining a pressure chamber therewith said housing translatable relative to said inlet, a flow limiter secured to translate with said housing between a raised position and a lowered position to establish said normal condition and override condition, respectively, a conduit to connect said pressure chamber with a port in said throttle bore intermediate said inlet and said idle position to allow the communication of engine pressure to said chamber when said throttle valve is not in its idle position and to prevent such communication when in said idle position, and a spring in said chamber for positioning said limiter in said raised position to establish said normal condition when engine pressure is not communicated to said chamber; and

d. throttle override valve control means connected in I valve to its idle position. 

1. A throttle control for controlling the speed of an internal combustion engine comprising: a. a carburetor having a throttle bore with an inlet admitting a flow of fluid, an outlet for communicating said fluid to said engine and communicating engine pressure to said throttle bore, a tHrottle valve pivotable in said throttle bore between a full open position and an idle position; b. throttle linkage means for normally pivoting said throttle valve between said full open and idle positions and including return spring means for normally biasing said throttle valve to said idle position, said throttle linkage means further including a throttle pedal having an operative condition for pivoting said throttle valve in a valve opening direction against the bias of said return spring means and having an inoperative condition for allowing said return spring means to normally return said throttle valve to said idle position; c. pneumatically operated valve means operated by said engine pressure and operable in a normal condition to fully open said inlet and alternatively in a throttle override condition to limit said fluid flow through said inlet so as to limit the speed of said engine to an idle speed; d. conduit means for connecting said pneumatically operated valve means and said throttle bore; and e. override control valve means connected in said conduit means and operated by said throttle pedal to control the communication of said engine pressure between said throttle bore and said pneumatically operated valve means to normally establish said normal condition with said throttle pedal in said operative condition and to establish said override condition with said throttle pedal in said inoperative condition and said throttle linkage prevented from returning said throttle valve to its idle position.
 2. A throttle control for controlling the speed of an internal combustion engine comprising: a. a carburetor having a throttle bore, an inlet for admitting a flow of fluid to said throttle bore, an outlet for communicating fluid to said engine and communicating engine pressure to said throttle bore, a throttle valve pivotable in said throttle bore between a full open position and an idle position; b. throttle linkage means for normally pivoting said throttle valve between said full open and idle positions and including return spring means for normally biasing said throttle valve means to said idle position, said throttle linkage means further including a throttle pedal having a depressed condition for pivoting said throttle valve in said valve opening direction against the return bias of said return spring means and having a released condition for allowing said return spring means to normally return said throttle valve to said idle position; c. differential pressure operated valve means operable in a normal condition to fully open said inlet and alternatively, in a throttle override condition to limit said fluid flow through said inlet so as to limit the speed of said engine to an idle speed, said valve means including a pressure chamber, pressure conduit means connected between said vacuum chamber and said throttle bore, and fluid flow limiter means translatable between a raised position and a lowered position relative to said inlet for establishing said normal condition when in said raised position and said override condition when in said lowered position; and d. throttle override control valve means connected in said pressure conduit means and operated by said throttle pedal to control the communication of said engine vacuum from said throttle bore to said pressure chamber through said vacuum conduit to normally establish said normal condition with said throttle pedal in said depressed condition and to establish said throttle override condition with said throttle pedal in said released condition and said throttle linkage means prevented from returning said throttle valve to said idle position.
 3. A throttle control for controlling the speed of an internal combustion engine comprising: a. a carburetor having a throttle bore, an inlet for admitting a flow of fluid to said throttle bore, an outlet for communicating said fluid to said engine and communicating engine pressure to said throttle bore, a throttle valve pivotable in said throttle bore between a full open position and an idle position; b. throttle linkage means for normally pivoting said throttle valve between said full open and said idle positions and including return spring means for normally biasing said throttle valve means to said idle position, said throttle linkage further including a throttle pedal having a depressed condition for pivoting said throttle valve in a valve opening direction against the return bias of said return spring means and having a release condition for allowing said return spring means to normally return said throttle valve to said idle position; c. differential pressure operated valve means operable in a normal condition to fully open said inlet and alternatively in a throttle override condition to limit said flow through said inlet so as to limit the speed of said engine to an idle speed, said valve means including a pressure chamber, a conduit connected between said pressure chamber and said throttle bore, fluid flow limiter means translatable between a raised position and a lowered position relative to said inlet for establishing said normal condition when in said raised position and said override condition when in said lowered position, and latch means for supporting said limiter means in a position intermediate said raised and lowered positions when the fluid flow through said inlet is less than a predetermined flow; and d. throttle override control valve means connected in said conduit and operated by said throttle pedal for controlling the communication of said engine pressure from said throttle bore to said pressure chamber to normally establish said normal condition with said throttle pedal in said depressed condition and to establish said throttle override condition with said throttle pedal in said released condition and said throttle linkage means prevented from returning said throttle valve to said idle position.
 4. A throttle control for controlling the speed of an internal combustion engine comprising: a. a carburetor having a throttle bore, an inlet for admitting a flow of air to said throttle bore, an outlet for communicating said flow to said engine while also communicating engine vacuum to said throttle bore, throttle valve means pivotable in said throttle bore between an idle position and a full open position; b. throttle linkage means including return spring means for normally biasing said throttle valve to said idle position and a throttle pedal having a depressed condition for pivoting said throttle valve in a throttle opening direction against the bias of said return spring means and having a released condition for allowing said return spring means to normally return said throttle valve to said idle position; c. differential pressure operated fluid motor means operable in a normal condition to fully open said inlet and in an alternative throttle override condition to limit the flow of fluid through said inlet so as to limit the speed of said engine to an idle speed, said fluid motor means fixedly supported above said inlet, a diaphragm retained by said body and defining a pressure chamber therewith, a flow limiter connected to said diaphragm and translatable between a raised position and a lowered position relative to said inlet to respectively establish said normal and override conditions, conduit means connecting said pressure chamber and a port in said throttle bore intermediate said idle position and said outlet for positioning said limiter in said raised position when the pressure in said chamber effects greater than a predetermined pressure differential across said diaphragm, and a spring in said pressure chamber for positioning said limiter in said lowered position when said pressure differential is less than said predetermined pressure differential; and d. throttle override control valve means connected in said conduit and operated by said throttle pedal, said control valve means, with said throttle pedal in said released condItion and with said throttle linkage prevented from returning said throttle valve to its idle position, having an open condition for reducing said pressure differential below said predetermined pressure differential to establish said override condition.
 5. A throttle control as set forth in claim 4 wherein, with said override control valve means in said open condition, said pressure chamber communicates freely with atmospheric pressure.
 6. A throttle control as set forth in claim 4 wherein, with said throttle override control valve means in said open condition, said pressure chamber communicates freely with said port.
 7. A throttle control for controlling the speed of an internal combustion engine comprising: a. a carburetor having a throttle bore, an inlet for admitting a flow of air to said throttle bore, an outlet for communicating said flow to said engine while also communicating engine pressure to said throttle bore, a throttle valve pivotable in said throttle bore between an idle position and an open position; b. throttle linkage means for pivoting said throttle valve between said idle and said open positions and including a return spring for normally biasing said throttle valve to said idle position and a throttle pedal having a depressed condition for normally pivoting said throttle valve in a throttle opening direction against the bias of said return spring and having a released condition for allowing said return spring to normally return said throttle valve to said idle position; c. differential pressure operated fluid motor means operable in a normal condition to fully open said inlet and in an alternative throttle override condition to limit the flow of said fluid through said inlet so as to limit the speed of said engine to an idle speed, said valve means including a diaphragm having a central portion fixedly supported above said inlet, a housing sealingly secured to said diaphragm and defining a pressure chamber therewith said housing translatable relative to said inlet, a flow limiter secured to translate with said housing between a raised position and a lowered position to establish said normal condition and override condition, respectively, a conduit to connect said pressure chamber with a port in said throttle bore intermediate said inlet and said idle position to allow the communication of engine pressure to said chamber when said throttle valve is not in its idle position and to prevent such communication when in said idle position, and a spring in said chamber for positioning said limiter in said raised position to establish said normal condition when engine pressure is not communicated to said chamber; and d. throttle override valve control means connected in said conduit and having a closed condition with said throttle pedal in said depressed condition to prevent communication of an engine pressure to said chamber with said throttle valve not in its idle position and having an open condition with said throttle pedal in said released condition for communicating engine pressure to said chamber to establish said override condition when said throttle linkage is prevented from returning said throttle valve to its idle position. 